GE LPS-O Instruction Manual page 269

13 XPRESSION BUILDER
The second type of timer is basically a pickup delay timer with a reset input/output feature. As shown in Figure
13–7: PICKUP DELAY TIMER, there are two inputs, two outputs, and a user selected pickup delay (in millisec-
onds). In its "initial" state with no inputs applied, both R and S are low (binary 0), the timer outputs RO and SO
are both low (binary 0). The timer starts counting when the S input is high (binary 1). When the count becomes
equal to the set time delay (1000 ms for our example), the SO output is set high (binary 1) and the RO output
is set low (binary 0). If the R input becomes high (binary 1) while the timer IS NOT counting, then both outputs
RO and SO are set low (binary 0) which returns the timer to its "initial state". See Table 13–1: PICKUP DELAY
TIMER TRUTH TABLE for a summary of the pickup delay timer function.
Table 13–1: PICKUP DELAY TIMER TRUTH TABLE
S R
L L
↑
L
X L
X H
↑
X
d) COUNTERS
The counter has two input line, one output line, and a user selected count threshold (in milliseconds) as shown
in Figure 13–8: COUNTER. A transition from low (binary 0) to high (binary 1) on the S input line increments the
counter by a value of one. The O output line is high (binary 1) when the accumulated count is equal to or
greater than the count threshold. If the O output line is low (binary 0), then the accumulated count is less than
the set value. A transition from low (binary 0) to high (binary 1) on the R input line resets the counter to zero.
GE Power Management
S
R
Figure 13–7: PICKUP DELAY TIMER
PREVIOUS TIMER STATE
NOT TIMING
NOT TIMING
TIMING DOWN
TIMING DOWN
NOT TIMING
S
0 0
R
Figure 13–8: COUNTER
LPS-O Line Protection System
13.2 DESIGN CONSIDERATIONS
1000
S O
R O
CURRENT TIMER STATE
NOT TIMING
TIMING DOWN
TIMER EXPIRED
TIMER RESET
NOT TIMING
5
0 0
O
RO SO
RO L
n-1
L L
L H
H L
L L
13-
7
13